Re: [PATCH v5 09/14] gtrace: Add RISC-V Trace ramsink driver

[Zane Leung]

On 8/10/2026 11:22 PM, Mayuresh Chitale wrote:

> +static size_t rvtrace_ramsink_copyto_auxbuf(struct gtrace_component *comp,
> +					    struct gtrace_perf_auxbuf *buf,
> +					    u64 *format)
> +{
> +	struct rvtrace_ramsink_priv *priv = dev_get_drvdata(&comp->dev);
> +	struct trace_buf src, dst;
> +	u32 wp_low, wp_high;
> +	size_t bytes = 0;
> +	bool wrap;
> +	u64 wp;
> +
> +	dst.base = buf->base;
> +	dst.len = buf->length;
> +	dst.cur = buf->pos;
> +	src.base = priv->va;
> +	src.len = priv->size;
> +	wp_low = gtrace_read32(comp->pdata, RVTRACE_RAMSINK_WPLOW_OFF);
> +	wp_high = gtrace_read32(comp->pdata, RVTRACE_RAMSINK_WPHIGH_OFF);
> +	wp = (u64)(wp_high) << 32 | wp_low;
> +	wrap = wp & RVTRACE_RAMSINK_WPLOW_WRAP;
> +	wp &= ~RVTRACE_RAMSINK_WPLOW_WRAP;
> +	if (wrap) {
> +		gtrace_write32(comp->pdata, lower_32_bits(priv->start),
> +				RVTRACE_RAMSINK_WPLOW_OFF);
> +		gtrace_write32(comp->pdata, upper_32_bits(priv->start),
> +				RVTRACE_RAMSINK_WPHIGH_OFF);
> +		src.cur = wp - priv->start;
> +		priv->prev_wp = priv->start;
> +		/*
> +		 * There is no way to tell if trRamWp wrapped around more than once. As a
> +		 * result priv->prev_wp can't be used and the entire buffer must be copied
> +		 * even though some data might be duplicated.
> +		 */
> +		bytes = priv->size;
> +	} else {
> +		src.cur =  priv->prev_wp - priv->start;
> +		bytes = wp - priv->prev_wp;
> +		priv->prev_wp = wp;
> +	}
> +
> +	tbuf_to_pbuf_copy(&src, &dst, bytes);
> +	dev_dbg(&comp->dev, "Copied %zu bytes\n", bytes);
> +	*format = PERF_AUX_FLAG_GTRACE_FORMAT_ETRACE;
> +	return bytes;
> +}

If the discovery of trace parameters is delegated to the user-space decoder according to the cover

letter, why are we explicitly setting PERF_AUX_FLAG_GTRACE_FORMAT_ETRACE here? Taking a step back,

the trace format should be determined by the  trTeControl's traceFormat rather than being hardcoded.